I would consider myself as roughly fitting into that category. I have a couple main suggestions for you.

1. Shoot a lot. Doesn't really matter what format it's in, what camera or lens you use, whatever. Just shoot. After shooting, don't look at your photos right away, for the same reason that film directors often take a vacation between finishing a film shoot and beginning editing. Shortly after shooting, you have an emotional attachment to certain images, and that bias can cloud your judgement of them. Step back, wait a while, and then look at what you've got. If you allow yourself to become more objective to your own work, you will often be able to more clearly see the merits and flaws.

2. Shoot all sorts of different things. Sample many different types of photography. If one scares you more than others, especially try that one. You don't necessarily have to stick with one you don't like, but at least give it a fair, honest try. Even if you end up never doing that style of photography again, you may still learn something valuable from that initial experience.

3. Force yourself to be creative. One of my favorite ways of doing this is going out shooting with only a single, prime lens. Having a strict limit on focal length often means that getting a particular shot I envision is very difficult, sometimes even impossible. This forces me to stop and think, "Ok, what exactly am I going for here? What is important in this shot, and how can I get it with what I have?" In forcing myself to struggle for the right image, I frequently come up with even better ideas than my initial ones, and I feel like I've grown as a photographer for it.